GLP-2 is a 33-amino-acid peptide derived from specific posttranslational processing of proglucagon in the enteroendocrine L cells of the intestine and in specific regions of the brainstem. It is co-secreted together with glucagon-like peptide 1 (GLP-1), oxyntomodulin and glicentin, in response to nutrient ingestion.
GLP-2 induces significant growth of the small intestinal mucosal epithelium via the stimulation of stem cell proliferation in the crypts and inhibition of apoptosis on the villi (Drucker et al. Proc Natl Acad Sci USA. 1996, 93:7911-6). GLP-2 also has growth effects on the colon. GLP-2 also inhibits gastric emptying and gastric acid secretion (Wojdemann et al. J Clin Endocrinol Metab. 1999, 84:2513-7), enhances intestinal barrier function (Benjamin et al. Gut. 2000, 47:112-9.), stimulates intestinal hexose transport via the upregulation of glucose transporters (Cheeseman, .Am J Physiol. 1997, R1965-71.), and increases intestinal blood flow (Guan et al. Gastroenterology. 2003, 125, 136-47).
GLP-2 binds to a single G protein-coupled receptor belonging to the class II glucagon secretin family. The GLP-2 receptor is expressed in the small intestine, colon and stomach, sites that are known to be responsive to GLP-2 (Yusta et al. .Gastroenterology. 2000, 119: 744-55). However, the target cell for GLP-2 receptor stimulation in the gastrointestinal tract remains unclear and the downstream intracellular mediators coupled to the GLP-2 receptor are poorly understood.
The demonstrated specific and beneficial effects of GLP-2 in the small intestine have raised much interest as to the use of GLP-2 in the treatment of intestinal disease or injury (Sinclair and Drucker, Physiology 2005: 357-65). Furthermore GLP-2 has been shown to prevent or reduce mucosal epithelial damage in a wide number of preclinical models of gut injury, including chemotherapy-induced enteritis, ischemia-reperfusion injury, dextran sulfate-induced colitis and genetic models of inflammatory bowel disease (Sinclair and Drucker Physiology 2005: 357-65).
Further, the expression of the GLP-2R mRNA in the stomach, (Yusta et al., 2000) together with the observation that GLP-2 reduces gastric motility and gastric acid secretion (Meier et al., 2006) provides ample evidence that the stomach is either directly or indirectly responsive to GLP-2. Nevertheless the use of GLP-2 or analogues of GLP-2 in conditions characterised by damage to the gastric lining has not yet being explored.
GLP-2 is secreted as a 33 amino acid peptide with the following sequence H-His-Ala-Asp-Gly-Ser-Phe-Ser-Asp-Glu-Met-Asn-Thr-Ile-Leu-Asp-Asn-Leu-Ala-Ala-Arg-Asp-Phe-Ile-Asn-Trp-Leu-Ile-Gln-Thr-Lys-Ile-Thr-Asp-OH (SEQ ID NO: 1). It is rapidly cleaved at the Alanine (A) in position 2 of the NH2 terminus to the inactive human GLP-2 (3-33) by the enzyme DPP IV. This rapid enzymatic degradation of GLP-2(1-33), in addition to renal clearance result in a half life of about 7 minutes for the peptide (Tavares et al., Am. J. Physiol. Endocrinol. Metab. 278:E134-E139, 2000).
In U.S. Pat. No. 5,994,500 (Drucker et al.) describes antagonists of GLP-2 and their effects on the growth of gastrointestinal tissue. It is suggested that the antagonists are formulated as pharmaceuticals to be used in the treatment of hyperplasia or to induce hypoplasia. In U.S. Pat. No. 5,994,500 the structure of mammalian GLP-2 has been altered by mutations, such as substitutions and deletions.
U.S. Pat. No. 6,184,208; U.S. Pat. No. 5,789,379 and U.S. Pat. No. 6,184,201 disclose GLP-2 analogues and their medical uses. These analogues are all obtained by substitutions and/or deletions of human GLP-2.
DaCambra et al. (Biochemistry 2000, 39, 8888-8894) describe the structural determinants for activity of GLP-2. Examples of such determinants are Phe6 and Thr5, which are referred to as crucial for GLP-2 receptor binding and activation.
In WO 97/39031 the GLP-2 analogue, [Gly2]GLP-2 is disclosed. Here the alanine in position 2 has been replaced with glycine to make the peptide resistant to DPP IV cleavage. The replacement of alanine is shown to increase the stability and potency of the peptide. The patent application describes how the GLP-2 analogue may be used against diseases associated with inflammation and destruction of the intestinal epithelial mucosa. These include massive small intestine resection, inflammatory bowel disease, chemotherapy and/or radiation induced enteritis and ischemic injury.
WO 02/066511 describes GLP-2 analogues having an extended half-life in vivo and their use as medicaments in the treatment of gastrointestinal disorders, such as inflammatory bowel diseases.
WO 01/41779 describes the use of h[Gly2]GLP-2 as a pretreatment for inhibiting chemotherapy induced apoptosis and promoting small intestinal epithelial cell survival.
All references cited herein are expressly incorporated by reference in their entirety. The use of GLP-2 or analogues of GLP-2 in the treatment of various diseases has been proposed by many scientists. However, there is still a need for improved and small intestine selective GLP-2 analogues.